Conventionally, an amorphous silicon (a-Si) film has been used mainly for a semiconductor film serving as a channel layer of a TFT (thin film transistor), which is a semiconductor device, in a liquid crystal display device, a thin film EL (electroluminescence) display device, an organic EL display device, or the like.
In recent years, as a material to replace a-Si, a complex oxide containing indium (In), gallium (Ga), and zinc (Zn), i.e., an In—Ga—Zn-based complex oxide (also referred to as “IGZO”) has been drawing attention. Such an IGZO-based oxide semiconductor can be expected to have higher carrier mobility than that in a-Si.
For example, Japanese Patent Laying-Open No. 2008-199005 (Patent Document 1) discloses that an oxide semiconductor film mainly composed of IGZO is formed through a sputtering method employing an oxide sintered material as a target.
Japanese Patent Laying-Open No. 2008-192721 (Patent Document 2) discloses an oxide sintered material containing In and tungsten (W) as materials suitably used in forming an oxide semiconductor film by the sputtering method or the like.
Moreover, Japanese Patent Laying-Open No. 09-071860 (Patent Document 3) discloses an oxide sintered material containing In and Zn.